Laundry treating appliance with controlled oscillating movement

ABSTRACT

Disclosed is a laundry treating appliance having a drum and a torsionally flexible drive mechanism. The drum simultaneously rotates in a first rotational direction and oscillates about an axis of rotation.

BACKGROUND OF THE INVENTION

A laundry treating appliance is a common household device for treatinglaundry in accordance with a preprogrammed treating cycle of operation.A subset of laundry treating appliances use a generally horizontallyrotating drum to define a chamber in which the laundry is received fortreatment according to the cycle of operation. The drum may be rotatedat a predetermined speed in a predetermined direction as required by thecycle. Some laundry treating appliances may reverse and/or oscillate thedirection of rotation in accordance with the preprogrammed cycle. Therotation of the drum may be used to impart mechanical action to thelaundry, which may be attributable to the lifting and falling of thelaundry as the drum is rotated and/or the relative sliding of individuallaundry items.

The mechanical action associated with the horizontally rotating drum isrelative low compared to other types of laundry appliances. Given thatthermal action, chemical action, and mechanical action are the threeprimary sources of cleaning action for the laundry, a laundry treatingappliance with a relatively low mechanical action will need to havegreater thermal action and/or chemical action to obtain the same degreeof cleaning.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, the invention is a laundry treating appliance and amethod of operating the laundry treating appliance, the appliance havinga drum rotatable about an axis of rotation; an electric motor having arotor; a torsionally flexible drive mechanism coupling the rotor withthe drum such that rotation of the motor effects a rotation of the drum;and a controller operably coupled with the motor and configured tosupply a control signal to the motor to effect a rotation of the drumcomprising a simultaneous general rotation in a first rotationaldirection and a oscillation about an axis of rotation.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic view of a laundry treating appliance according toa first embodiment of the invention.

FIG. 2 is a perspective view of an exemplary laundry treating appliancein the form of a washing machine according to a second embodiment of theinvention.

FIG. 3 is a schematic view of the washing machine of FIG. 2.

FIG. 4 is a perspective cross-sectional view of an oscillation mechanismand a motor according to a third embodiment of the invention.

FIG. 5 is a schematic illustration of a complex rotation of a drumaccording to a fourth embodiment of the invention.

FIG. 6 is an example of a complex control signal according to the fourthembodiment of the invention.

FIG. 7 is a schematic illustration of a complex rotation of a drumaccording to a fifth embodiment of the invention.

FIG. 8 is an example of a complex control signal according to the fifthembodiment of the invention.

FIG. 9 is an illustration of a motor torque signal according to a sixthembodiment of the invention.

FIG. 10 is an illustration of a rotor speed and drum speed signalaccording to the application of the motor torque signal of the sixthembodiment of the invention.

FIG. 11 is an illustration of a tangential acceleration force accordingto the application of the motor torque signal of the sixth embodiment ofthe invention.

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

Referring now to the figures, FIG. 1 is a schematic view of a laundrytreating appliance 1 according to a first embodiment of the invention.The laundry treating appliance 1 and methods described herein may beused with any suitable laundry treating appliance, such as any machinethat treats fabrics, and examples of the laundry treating appliance mayinclude, but are not limited to, a washing machine, includingtop-loading, front-loading, vertical axis, and horizontal axis washingmachines; a dryer, such as a tumble dryer or a stationary dryer,including top-loading dryers and front-loading dryers; a combinationwashing machine and dryer; a tumbling or stationaryrefreshing/revitalizing machine; an extractor; a non-aqueous washingapparatus; and a revitalizing machine.

For illustrative purposes, the different embodiments will be describedwith respect to a washing machine with the fabric being a laundry load,with it being understood that the invention may be used with other typesof laundry treating appliances for treating fabric. The laundry treatingappliance 1 may have a stationary tub 2, a drum 4 rotatable about an inat least one of rotational directions about an axis of rotation, anoscillation mechanism 6 rotationally oscillating the drum 4 about theaxis of rotation and a motor 8 operably coupled with the drum 4 torotate the drum 4 at various speeds in either a first rotationaldirection and a second rotational direction, opposite the firstrotational direction. The oscillating mechanism 6 may be couple with themotor 8 and/or may couple the motor 8 with the drum 4. Shownconfiguration of the laundry treating appliance 1 oscillates the drum 4about the axis of rotation while the drum 4 is being rotated at thepredetermined operating speed.

Washing machines are typically categorized as either a vertical axiswashing machine or a horizontal axis washing machine. As used herein,the “vertical axis” washing machine refers to a washing machine having arotatable drum that rotates about a generally vertical axis relative toa surface that supports the washing machine. In some vertical axiswashing machines, the drum rotates about a vertical axis generallyperpendicular to a surface that supports the washing machine. However,the rotational axis need not be perfectly vertical or perpendicular tothe surface. The drum can rotate about an axis inclined relative to thevertical axis. As used herein, the “horizontal axis” washing machinerefers to a washing machine having a rotatable drum that rotates about agenerally horizontal axis relative to a surface that supports thewashing machine. In some horizontal axis washing machines, the drumrotates about a horizontal axis generally parallel to a surface thatsupports the washing machine. However, the rotational axis need not beperfectly horizontal or parallel to the surface. The drum can rotateabout an axis inclined relative to the horizontal axis, with fifteendegrees of inclination being one example of inclination.

In the laundry treating appliance 1, the laundry is cleaned by threemain sources of energy: chemical, thermal, and mechanical. Mechanicalenergy can further be divided into two components: clothes-to-clothesfriction and the falling action associated with the tumbling of clothesdue to the rotation of the drum 4. Depending on the variouscharacteristics of the treating appliance 1, such as the size of thedrum 4, the size of the laundry load, and the control signal, therotation of the drum 4 may result in various types of laundry loadmovement inside the drum 4. For example, the laundry load may undergo atleast one of tumbling, rolling (also called balling), sliding,satellizing (also called plastering), and combinations thereof. Duringtumbling, the fabric items in the drum 4 rotate with the drum 4 from alowest location of the drum 4 towards a highest location of the drum 4,but fall back to the lowest location before reaching the highestlocation. The terms tumbling, rolling, sliding and satellizing are termsof art that may be used to describe the motion of some or all of thefabric items forming the laundry load. However, not all of the fabricitems forming the laundry load need exhibit the motion for the laundryload to be described accordingly.

Referring now to FIG. 2, which is a perspective view of a laundrytreating appliance in the form of a washing machine according to asecond embodiment. As illustrated, the clothes washer 10 may have acabinet 20 in which is provided a controller 22 that may receive aninput from a user and/or provide information to a user through a userinterface 24 for selecting a cycle of operation, including operatingparameters for the selected cycle, and controlling the operation of theclothes washer 10 to implement the selected cycle of operation.

Referring now to FIG. 3, which is a schematic view of the laundrytreating appliance 10 of FIG. 2, it is shown an imperforate tub 12 and aperforated drum 14 may be located within the interior of the cabinet 20.The tub 12 and the drum 14 may be mounted in the cabinet 20 such thatthe drum 14 can rotate relative to the tub 12. The drum 14 may define awash chamber 26 for receiving laundry that has an open face that may beselectively closed by a door 28. The drum 14 further may have one ormore baffles 30, which are sometimes referred to as lifters. The baffles30 facilitate the tumbling action of the fabric load within the drum 14as the drum 14 rotates about the rotational axis. Additionally, theinterior surface of the drum 14 and/or the surface of the baffles 30 maybe textured to increase a mutual friction between the drum 14 andlaundry improving the mechanical action given to the laundry.

An automatic motor 18 may be coupled to the drum 14 via a drive shaft 32to rotate the drum 14 at various speeds in either rotational direction.The motor 18 may be a direct drive motor, for example, a brushlesspermanent magnet (BPM) motor, an induction motor, a permanent splitcapacitor (PSC) motor, etc. Alternately, the motor 18 may be indirectlycoupled with the drive shaft 32 via for example a belt, as is known inthe art.

The washing machine 10 may further include a liquid supply andrecirculation system. Liquid, such as wash aid, which is typicallywater, alone or in a mixture with other wash aids, may be supplied tothe washing machine 10 from a water supply 40 in the case of water, suchas a household water supply. A supply conduit 42 may fluidly couple thewater supply 40 to a detergent dispenser 44. An inlet valve 46 maycontrol flow of the liquid from the water supply 40 and through thesupply conduit 42 to the detergent dispenser 44. A liquid conduit 48 mayfluidly couple the detergent dispenser 44 with the tub 12. The liquidconduit 48 may couple with the tub 12 at any suitable location on thetub 12 and is shown as being coupled to a front wall of the tub 12 inFIG. 3 for exemplary purposes. The liquid that flows from the detergentdispenser 44 through the liquid conduit 48 to the tub 12 typicallyenters a space between the tub 12 and the drum 14 and may flow bygravity to a sump 50 formed in part by a lower portion of the tub 12.The sump 50 may also be formed by a sump conduit 52 that may fluidlycouple the lower portion of the tub 12 to a pump 54. The pump 54 maydirect fluid to a drain conduit 56, which may drain the liquid from thewashing machine 10, or to a recirculation conduit 58, which mayterminate at a recirculation inlet 60. The recirculation inlet 60 maydirect the liquid from the recirculation conduit 58 into the drum 18.The recirculation inlet 60 may introduce the liquid into the drum 14 inany suitable manner, such as by spraying, dripping, or providing asteady flow of the liquid. A heating element 61 may be provided in thesump 50 to heat the liquid.

The liquid supply and recirculation system may further include one ormore devices for heating the liquid; exemplary devices include sumpheaters and steam generators. Additionally, the liquid supply andrecirculation system may differ from the configuration shown in FIG. 3,such as by inclusion of other valves, conduits, wash aid dispensers,sensors, such as water level sensors and temperature sensors, and thelike, to control the flow of liquid through the washing machine 10 andfor the introduction of more than one type of detergent/wash aid.Further, the liquid supply and recirculation system need not include therecirculation portion of the system or may include other types ofrecirculation systems.

A steam generator 45 may be provided to supply steam to the treatingchamber 26, either directly into the drum 14 or indirectly through thetub 12 as illustrated. The valve 46 may also be used to control thesupply of water to the steam generator 45. The steam generator 45 isillustrated as a flow through steam generator, but may be other types,including a tank type steam generator. Alternatively, the heatingelement 61 may be used to generate steam in place of or in addition tothe steam generator 45. The steam generator 45 is controlled by thecontroller 22 and may be used to heat to the laundry as part of a cycleof operation, much in the same manner as heating element 61. The steamgenerator 45 may also be used to introduce steam to treat the laundry ascompared to merely heating the laundry.

In case of a dryer, an air flow system (not shown) is used, having ablower to first draw air across a heating element and into the drum,through a lint filter, and finally out through an exhaust conduit thatis connected to an exhaust vent system leading out of the house.

Turning now to FIG. 4, an oscillation mechanism 16 is illustrated in aperspective cross-sectional view of the oscillation mechanism 16 andmotor 18 according to a third embodiment of the invention. Theillustrated motor 18 is a direct drive motor which may have a rotor 34and a stator 36. A tub bearing 62 and a drum support 64 may also beprovided as part of the rotational coupling of the drum 14 to the tub12. The oscillating mechanism 16 according to one embodiment may beimplemented as a rotationally, torsionally flexible drive shaft 32coupling the motor 18 to the drum 14 via the drum support 64. The driveshaft 36 may be made of any material and design having a suitabletorsional stiffness. High carbon steel is a non-limiting example of thesuitable material. The torsional stiffness of the drive shaft 32 may beselected based on the anticipated combined inertia the drum 14 with theload of laundry and is a function of the drive shaft design. The washingmachine is normally designed to wash laundry loads within apredetermined weight range, which can be used to select a torsionalstiffness suitable for a particular washing machine. Other factorsrelated to the anticipated inertial for the anticipated weight range mayalso be taken into account, for example, the radius of the drum and themass of the drum.

As illustrated in FIG. 4, one method of setting the torsional stiffnessis to control the cross section of the drive shaft 32. The drive shaft32 has a reduced cross-sectional portion 70 between a first end of thedrive shaft 72 coupled with the motor 18 and a second end of the driveshaft 74 coupled with the drum 14. This reduced cross-sectional portion70 may provide a suitable torsional flexibility enabling the shaft 18 toact as the oscillating mechanism 16.

The controller 22 may be operably coupled with the motor 18 and theoscillating mechanism 16 and configured to supply a control signal toboth the motor 18 and the oscillating mechanism 16 to effect therotation of the drum 14. Alternatively, a separate controller (notshown) may be used to control an operation of the oscillating mechanism16.

The controller 22 also may be a combination of a machine controller andmotor controller within one physical location or a practicalimplementation may require their physical separation. The type andconfiguration of the controller 22 are not germane to the invention. Anysuitable control system capable of outputting control signals to themotor 18 and to the oscillating mechanism 16 may be used. The controller22 may be configured to supply a control signal to effect the rotationof the drum 14 about the axis of rotation O. The oscillation may beobtained by rotating the drum 14 in such a manner to induce oscillationsin the drive shaft 32, with the oscillation generating the forcesdescribed by force vectors below.

FIG. 5 schematically shows an oscillating rotation according to a fourthembodiment of the present invention. The illustrated rotation is asuperimposed general rotation shown by a force vector α in the firstrotational direction A and an oscillating rotation shown by a forcevector β in alternating rotational directions A and B. The combinationof these forces results in the rotation of the drum 14 in the directionA with slight oscillations between directions A and B. The magnitude ofthe force vector β is selected such that the overlying oscillations onthe continuous rotation will impart to the laundry 66 in the drum atemporary force sufficient to overcome the frictional force between thelaundry 66 and the drum to cause sliding movement of the laundry 66 inthe directions A and/or B relative to the drum. This sliding movement ofthe laundry 66 provides a better mechanical cleaning action, especiallyif the interior surface of the drum 14 and/or the outer surface of thebaffles 30 are textured.

The control signal from the controller 22 may be a composite signal offirst and second superimposed signals, where the first signal effectsthe general rotation of the drum in the first rotational direction A andthe second signal effects the oscillation of the drum about the axis ofrotation O. The first signal may be selected to effect a predeterminedoperating speed of the drum 14 in accordance with a particular phase ofthe cycle of operation. The predetermined operating speed of the drum 14may be, for example, a constant speed, an accelerating/deceleratingspeed, a tumbling speed, etc., or a combination of thereof. The secondsignal may be a sinusoidal wave form, a step wave form to cycle themotor 14 between ON and OFF states, a step wave form to cycle the motor14 between a full motor torque and less than the full motor torquestates, a signal accelerating and decelerating the motor 14, or otherhigh frequency signals effecting the drum 14 to oscillate.

FIG. 6 shows an example of a composite control signal superimposed ofthe first signal effecting the drum 14 to rotate at the a constantpredetermined operating speed, and the second signal having a sinusoidalwave form effecting the drum 14 to oscillate about the axis of rotationO. This type of rotation may correspond to the rotation shown in theFIG. 5.

FIG. 7 schematically shows an oscillating rotation according to a fifthembodiment of the present invention. Similar to the fourth embodiment,the illustrated rotation is a superimposed general rotation shown by aforce vector α in a first rotational direction A in combination with arepeating and discrete force vector β in a second rotational directionB. The combination of the two forces creates a type stutter rotation inthe direction A. In other words, the general rotation in direction Awith slight interruptions in the continuous rotation of the drum 14. Themagnitude of the force vector β should be great enough such that theresulting interruptions in the continuous rotation will impart to thelaundry 66 in the drum a temporary force sufficient to overcome thefrictional force between the laundry 66 and the drum to cause slidingmovement of the laundry 66 in the directions A and/or B relative to thedrum.

FIG. 8 illustrates an example of a composite control signal superimposedof the first signal effecting the drum 14 to rotate at the a constantpredetermined operating speed, and the second signal having a step waveform effecting the drum 14 to slightly stutter. The illustratedsuperimposed signal may correspond to the type rotation shown in theFIG. 7.

The drum 14 and the laundry load in the drum collectively define asystem mass having a resonance frequency and the oscillation mechanism16 may rotationally oscillate the mass at a rate sufficiently close tothe resonance frequency to initiate the excitation of a resonanceresponse of the system mass. In a case of the drum oscillation at theresonance frequency, a smaller amount of force is required to reachgreater amplitude of the drum oscillation and a motor force feels onlylosses of that resonant system. The resonance of the system may occur ata natural frequency that is higher than the predetermined operatingspeed of the drum 14.

Similarly, the resonance may be excited by the controller 22superimposing a force in the resonant frequency to the normal runningforces of the motor 18. Using the resonance frequency will decrease anotherwise large force needed to rotate the drum 14. It will beunderstood, that it is within the scope of the present invention to useother types of oscillation mechanism 16 to enable slightinterruptions/oscillations in the continuous rotation of the drum 14about the axis of rotation O.

For example, the oscillation mechanism 16 may be embodied as a torsionspring system, defining a resonant system between the mass of the drum14 and the mass of the rotor 34. When the oscillation mechanism 16 isembodied as a torsion spring system, the resonance frequency f₀ of thesystem may be based on the stiffness K of the drive shaft 70 and theinertia of the drum J_(D) and rotor J_(R) according to equation (1)below.

$\begin{matrix}{f_{0} = {\frac{1}{2\pi}\sqrt{K\; \frac{J_{R} + J_{D}}{J_{R} \times J_{D}}}}} & (1)\end{matrix}$

For example, for an exemplary washing machine where J_(D)=1.26 kg*m2,J_(R)=0.138 kg*m² and K of the drive shift is 529.8 N*m/rad, theresonance frequency of the system may be determined using equation (1)as 10.4 Hz. The determined resonance frequency can be used to apply acomposite control signal in which a second signal, such as describedabove with respect to FIGS. 6 and 8, for example, is applied at afrequency of 10.4 Hz to effect an oscillation of the drum 14 about theaxis of rotation O. It will be noted that the resonance frequency willvary from machine to machine and this example is meant to beillustrative and not limiting.

The previously described washing machine 10 provides the structurenecessary for the implementation of a method of applying mechanicalenergy to the load of laundry in the laundry treating appliance 10 withthe controller 22 configured to supply the motor 18 with a compositecontrol signal to control the applied torque. The controller 22 maysupply the motor 18 with a composite signal including a first torquesignal to rotate the drum 14 at a predetermined operating speed and asecond torque signal to apply an oscillating rotational force. Anexemplary method 100 will now be described as illustrated by FIGS. 9-11.FIGS. 9-11 are not necessarily indicative of real data and are forillustrative purposes only for the purpose of describing an embodimentof the invention and are not meant to limit the invention in any manner.

As discussed above, the drum 14 and rotor 34 may be considered asdefining a resonant system in which the resonance frequency f₀ of thesystem may be determined based on equation (1). The controller 22 mayuse the determined resonance frequency to determine a frequency at whichto apply the second signal in the form of a dynamic torque to the drum14. For example, the controller 22 may use the resonance frequency todetermine a frequency at which to apply a sinusoidal torque signal. Themass of the rotor 34 may be predetermined and stored in a memoryaccessible by the controller 22 and used to determine the inertia J_(R)of the rotor 34. The inertia of the drum 14 may be determined at anypoint during a cycle of operation after the laundry has been placed inthe drum 14 using any known method, non-limiting examples of whichinclude determining the time it takes to accelerate between twopre-determined speeds under a constant applied torque, determining thetime to decelerate from a first speed to a second speed and measuringthe torque required to rotate a load at a predetermined constant speed.

The amplitude of the dynamic torque signal may be selected by thecontroller 22 to provide a predetermined maximum tangential accelerationa_(t) to effect the sliding movement of the laundry within the drum 14.The laundry may be excited to slide within the drum 14 if the force tomove the laundry relative to the drum F_(at) is greater than thefrictional force between the laundry and the drum _(friction). F_(at) isequal to the tangential acceleration a_(t) times the mass of the laundryand F_(friction) is equal to the fabric friction constant μ times theacceleration a and mass of the laundry, the acceleration being equal tothe maximum vertical acceleration due to gravity and the centrifugalacceleration. The fabric friction constant μ may be determinedexperimentally or empirically for different types of fabric such ascotton, silk and denim, for example, and stored within a memoryaccessible by the controller 22. The type of fabric comprising the loadmay be determined manually, such as by user input through a userinterface, or automatically by the washing machine 10 according to anyknown method, such as based on the absorbency of the load, for example.

FIG. 9 illustrates an example of a motor torque signal in which asinusoidal torque signal 110 is applied. As illustrated in FIG. 9, afirst, constant motor torque signal 108 of approximately 19.1 N*m isapplied to rotate the drum 14 in a first direction, such as clockwise,for example, at a predetermined operating speed. Any suitable motortorque magnitude may be selected to rotate a given load at a desiredpredetermined speed based on one or more operating parameters such asthe selected operating cycle, the amount of laundry and the type oflaundry and/or one or more characteristics of the system such as thesize of the drum 14, the size of the motor 18 and the stiffness of thedrive shaft 70, for example. At approximately 2.5 seconds a dynamictorque signal in the form of a sinusoidal torque signal 110 having anamplitude of approximately 0.3 N*m is applied to the motor 18. Thesinusoidal torque signal 110 may be applied at any suitable time duringa course of operation. The sinusoidal torque signal 110 results inrotation of the drum 14 in the first direction with slight oscillationsbetween the first direction and a second direction opposite the first.For example, if the drum 14 is rotating clockwise due to the applicationof a constant motor torque, the application of a sinusoidal torquesignal results in the drum rotating clockwise with slight clockwise andcounter-clockwise oscillations.

The amplitude of the applied sinusoidal torque signal 110 may bedetermined as described above based on the mass and type of fabric ofthe laundry. The frequency of the sinusoidal torque signal 110 may beselected based on the stiffness K of the drive shaft 70 and the inertiaof the drum J_(D) and rotor J_(R) as discussed above with reference toequation (1) to generate resonance between the rotor 34 and the drum 14.Generating resonance between the rotor 34 and the drum 14 may result inless force being required to achieve a predetermined amplitude of drumoscillation.

As illustrated in FIG. 10, the sinusoidal torque signal 110 results inoscillation of the rotor 34 in alternating directions, which results inoscillation of the rotor speed above and below a set rotation speed asillustrated by rotor speed signal 112. As illustrated in FIG. 10, thespeed of the rotor 34 is brought up to approximately 40 rpm as a resultof the applied constant motor torque 108 and the application of thesinusoidal torque signal 110 around 2.5 sec results in an oscillation ofthe rotor speed above and below 40 rpm. The oscillations of the rotor 34may be transferred through the drive shaft 70 to the drum 14 whichcauses the drum 14 to rotate at approximately 40 rpm with slightoscillations above and below 40 rpm as illustrated by drum speed signal114. The application of the sinusoidal torque signal 110 near theresonance frequency of the system may provide a more efficient transferof the sinusoidal torque signal 110 through the rotor 34 to the drum 14such that a smaller alternating torque is required to oscillate the drum14 than may be necessary if the sinusoidal torque signal was applied ata frequency not near the resonance frequency of the system.

FIG. 11 illustrates a tangential acceleration signal 116 representativeof a tangential acceleration that may be experienced by a laundry loadin the drum 14 when the drum 14 is rotated according to the torquesignals 108, 110 illustrated in FIG. 9. In this example, the maximumtangential acceleration experienced by the laundry load as a result ofthe applied sinusoidal torque signal 110 is approximately 2.35 m/s². Asdiscussed above, if the maximum tangential acceleration of 2.35 m/s²provides an F_(at) larger than the F_(friction) between the laundry loadand the interior of the drum 14, then the laundry load may slide withinthe drum 14 as the drum 14 is rotated and oscillated. This slidingmovement of the laundry load may provide an improved mechanical cleaningaction.

The dynamic torque signal may be applied one or more times at anysuitable time during the course of a cycle of operation to providesliding movement of the laundry load relative to the drum 14 to improvethe mechanical cleaning action during a course of operation. The method100 may also be used to apply the dynamic torque signal as a step waveform, similar to that described with respect to FIGS. 7 and 8.

While the method 100 is described as generating a dynamic torque signal110 at the resonance frequency of the system based on equation (1), itis also within the scope of the invention for the dynamic torque signalto be generated at a frequency based on a harmonic of the drum rotationfrequency. For example, if the drum 14 is rotating at 40 rpm or 0.667Hz, the frequency for generating a dynamic torque signal may be the14^(th) harmonic or approximately 10 Hz. Alternatively, an independentfrequency may be superimposed on the torque signal.

It is also within the scope of the invention for the controller 22 tomonitor the amplitude of the rotor oscillations and adjust the frequencyof the applied dynamic torque signal to achieve a desired amplitude. Theamplitude of the rotor oscillations may be determined based on the backEMF from the motor or the current fluctuation. The controller 22 mayalso use the determined amplitude to determine when resonance starts orwhen the amplitude is at a maximum. This information may then be used bythe controller 22 to set one or more operating parameters, such as howlong to apply the dynamic torque signal or when to apply a treatmentchemistry, for example.

While the invention has been specifically described in connection withcertain specific embodiments thereof, it is to be understood that thisis by way of illustration and not of limitation. Reasonable variationand modification are possible within the scope of the forgoingdisclosure and drawings without departing from the spirit of theinvention which is defined in the appended claims.

1-16. (canceled)
 17. A method of applying mechanical energy to a load oflaundry in a treating chamber of a laundry treating appliance having arotatable drum defining the treating chamber and rotatable about an axisof rotation, a motor configured to rotate the drum, and a controllerconfigured to supply the motor with a control signal to control therotational speed of the drum, the method comprising: rotating the drumin a first rotational direction at a predetermined operating speed; andoscillating the drum about an axis of rotation to effect a sliding ofthe laundry relative to the drum while the drum is rotated in the firstrotational direction at the predetermined operating speed.
 18. Themethod of claim 17 wherein the predetermined operating speed is aconstant speed.
 19. The method of claim 17 wherein the predeterminedoperating speed is a tumbling speed.
 20. The method of claim 19 whereinthe oscillating the drum comprises oscillating the drum at a frequencygreater than the tumbling speed.
 21. The method of claim 17 wherein thesupplying the motor with a control signal comprises supplyingsuperimposed first and second control signals, with the first controlsignal effecting the rotation of the drum at the predetermined operatingspeed and the second control signal effecting the oscillating of thedrum.
 22. The method of claim 21 wherein the second control signal isselected to oscillate the drum at a frequency causing excitation of atorsional resonance of a drive shaft coupling the motor and the drum.23. The method of claim 22 wherein the torsional resonance is determinedbased on the collective rotational inertia of the drum and the load oflaundry in the treating chamber.
 24. The method of claim 21 wherein thesecond control signal comprises a sinusoidal wave form.
 25. The methodof claim 21 wherein the second signal comprises a step wave form tocycle the motor between ON and OFF states.
 26. The method of claim 21wherein the second signal accelerates and decelerates the motor.
 27. Themethod of claim 17 wherein the oscillating the drum about an axis ofrotation occurs at a frequency causing excitation of a resonance of adrive shaft coupling the motor and the drum.
 28. The method of claim 17wherein the oscillation about the axis of rotation comprises rotationbetween the first and a second rotational direction, opposite the firstrotational direction.